@SquareDaff - as an aside how have you found riding a 650b size?
My C2W purchase is a 2014 Whyte 805 which also runs on 650b wheels. I can echo the 'balloon' comment. They've been OK but hard work uphill; having done about 350 miles I'm finding I don't use it anywhere near as much as I'd thought. That's partly because the road/cross bikes are easier and I'm using the basic 26" wheel MTB I have instead.
I agree with you re: the Cross bikes being easier. I can get an average of a fraction under 20mph on my Boardman CX - but only around 16mph on the MTB (on road). Maybe due to the weight and the balloon effect which is quite energy sapping.
Now I've got used to the higher COG I'm finding it quite agile at lower speeds, which is obviously what it's designed for. On the roads it rarely gets off the big chain ring. The commute in on Tuesday was a "fault finding" ride and I ended up with a list of minor adjustments that I'll need to make this weekend. Once they're done I'll give it a spin on something more suitable to it's role.
As for the 650b wheelsize - I'm only 5ft 6ins and for how I'll use it, it seemed the ideal choice. At speeds, once you get over the initial shock of the slight "imbalance movement" (for want of a better description) it seems quite responsive to power throughput and turns into corners well. Obviously they drop speed quite quickly - but I'd suspect thats primarily down to tyre choice.
I should get quite a bit of leisure use out of it in the summer months - but expect it'll come into its own in the winter months - especially if we ever get levels of snow like we did a couple of years ago. I might also use it as a "fitness aid". I was done in after about 15 miles of riding the MB, yet can easilg ride 100+ on my road bike.